Typically, gravity feed blood filtration devices require user manipulation of vent filters during the filtration process. The manipulation of the vent filters must occur at the proper time during the filtration process or the system will not filter properly and blood being filtered may be rendered unusable. Since, user manipulation of vent filters is time consuming and costly, it is desirable to achieve a liquid filtration device which may filter blood without the manipulation of vent filters or filtration devices. Moreover, blood filtration devices usually allow liquid to remain within the filtration device after filtration has occurred. This remaining liquid, referred to as a hold up volume, is often greater than the desired maximum amount. Also, blood filtration devices allow an undesirably high amount of air that is purged therefrom to be left in the receiving blood bag.
The filtration device disclosed in U.S. Ser. No. 08/209,523, U.S. Pat. No. 5,472,605 and entitled "A Filtration Device Usable for Removal of Leukocytes and Other Blood Components" filed Mar. 10, 1994, which is hereby incorporated by reference and made a part of the disclosure herein, overcomes the aforementioned vent filter manipulation problem. However, it is desirable to reduce the hold up volume of this device and to reduce the manufacturing cost thereof, while maintaining an acceptable total filtration time. It is also desirable to achieve a filtration device which does not require draining of the outlet tubing at the end of the filtration cycle.
Blood filtration devices typically do not have features which prevent the tubing attached thereto from becoming kinked. It is, therefore, desirable to achieve a liquid filtration device which filters blood without the manipulation of vent filters, minimizes hold up volume, that minimizes the volume of air that is added to the receiving blood bag, that reduces manufacturing cost and also reduces the possibility of kinked tubing when the device is assembled into a filtration system and packaged for shipping.